Improvement in duplex telegraph-keys



PATENT OFFICE.

JOSEPH B. STEARNS, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT IN DUPLEX TELEGRAPH-KEYS.

Specification forming part of Letters Patent No. 136,875, dated March 18, 1873.

(Men D.

- graph-key, which I call a wedge-key, by means of which a galvanic battery may be introduced into and removed from a circuit so that a current can be transmitted to a distant station without breaking or interrupting the circuit from that station;

The accompanying drawing forming a part I of this specification represents my invention,

Figurel being a front elevation of my improved key; Fig. 2 being a plan, and Fig. 3 an end elevation, of the same. Fig. 4, sheet2, is a diagram showing the battery and its connection.

Like letters in the figures refer to similar parts.

Description of the Drawing.

A is a metallic lever, similar to the lever of the common telegraph-key, which is pivoted in the usual manner upon asuitable base, and is provided at one extremity with the usual finger-knob H. B is a bar of some insulating substance, such as hard rubber, pivoted at right angles to the opposite extremity of the lever A. This bar is wedge-shaped at its upper extremity, and has attached to it, one on each side, plates of metal 0 O. The plates of metal are connected respectively to the opposite poles of a galvanic battery, L B, by the screw constructions K K, and wires F F. D D are two flat metallic springs, which are attached at their upper ends to a block of insulating material, M, supported on a proper standard of metal, and at their lower ends rest uponthe wed ge-shaped insulating'portion of the bar B, one on each side, but do no touch the metallic plates 0 0. Upon one o these metallic springs, D, is a platinum point; I, which rests againsta metallic projection, G, extending out from the standard S, so that when the bar B is depressed the point I and projection G are in contact, and the circuit is completed through them. The circuit from the line to earth is completed through screwconnection L, wire L, upper portion of metallic plate D, wire-O, in Fig. 3, standard S, metallic projection G, platinum point I, metallic spring D, wire E, and screw-connection E, to earth. The resistance of the wire 0 is equal to that of the battery L B.

The operation of the key is as follows On depressing the knob of H of the lever A to send a signal, the bar B is elevated, and its wedge-shaped portion enters between the metallic springs D D, and separates them slightly. This breaks the circuit at I, but at the same time the metallic springs D D come into contact with the metallic plates 0 O on each side of the bar B, and the battery L B is thrown into the circuit through K F 0 D L back through E E D O F K to battery, and a signal is transmitted. Owing to the fact that the resistance at O is the same as that of the battery, the resistance of the circuit remains unchanged.

What I claim as my invention, and desire to secure by Letters Patent of the United States, is-

. The combination of the lever A, insulatingbar B, metallic plates 0 O, metallic springs D D, insulating-block M, projection G, and connecting-wires F F L E, and O, substantially as and for the purpose as set forth.

JOSEPH B. STEARISS.

. Witnesses:

A. L. HAYES, WILLIAM A. HAYES, JR. 

